1. Field of the Invention
The present invention relates nuclear reactor vessels, and in particular to a tool that may be used to simplify and facilitate the removal and replacement of a Local Power Range Monitor (LPRM) in a nuclear reactor vessel.
2. Related Art
Local Power Range Monitors (LPRMs) are used in nuclear reactor vessels to monitor the power output of nuclear fuel which is a direct indication of the amount of power that the nuclear power plant is producing. LPRMs are a vital part of nuclear reactor function and need to be replaced from time to time. Typical LPRMs are approx 60 ft long and each include a number of axially spaced neutron detectors. LPRMs extend within a vessel incore housing from an LPRM assembly flange that is located under the reactor vessel where they are secured in place up through the fuel core of the reactor and to the reactor top guide.
Before an LPRM can be exchanged, it must be disconnected from its vessel incore housing from a position under the reactor vessel. The LPRM exchange process first requires an under vessel team to go under the reactor vessel and remove an LPRM assembly seal and an LPRM assembly nut that are coupled to the LPRM assembly flange and that secure the LPRM in place in order to free the LPRM from its vessel incore housing. Once this is accomplished, a refuel floor team pulls the LPRM from the reactor core for disposal. The refuel floor team will then install the new LPRM and the under vessel team will reinstall the LPRM assembly nut and LPRM assembly seal, thus securing the new LPRM in place.
Currently, three tools must be carried to the under vessel area in order to free the LPRM as just described. Those tools includes one tool for removing the seal and two different tools for removing the nut. Two tools must be taken for the nut because two different size nuts can be used on an LPRM assembly and it is typically not known in advance which size nut is installed on any particular LPRM assembly. The actual nut size cannot be determined until the team tries to put a tool on the nut.
There is thus room for improvement in the area of removal and replacement of a LPRMs in nuclear reactor vessels. In particular, there is a need for a tool that simplifies and facilitates the removal and replacement of LPRMs in nuclear reactor vessels.